Fabrics which possess conductive properties have been produced by coating a fiber-forming nonconductive polymer with a conductive layer composed of a polymer containing conductive particles, e.g., metal particles such as carbon black. Carbon black-containing conductive fibers are difficult and expensive to produce and possess a color which is limited to black or gray.
Conductive fibers are manufactured using a drawing step which elongates the fiber and during which the chain structure of the conductive particles within the fiber is often disrupted. Often, the drawing step results in a decrease and sometimes a substantial loss of conductivity of the fiber.
U.S. Pat. Nos. 4,420,534 and 4,457,973, disclose conductive composite filaments which are formed by conjugate-spinning a conductive component which includes electrically conductive titanium, tin, zinc, iron, aluminum or magnesium oxide particles and a thermoplastic polymer and/or a solvent-soluble polymer and a non-conductive fiber-forming polymer. Conductivity is maximized by maximizing dispersion of the conductive particle in the polymer using dispersants. In addition, these patents stress that particles conferring extreme whiteness are preferred.
Prior art disclosures of metal oxides include preparations of spherical zinc or titanium oxide particles (U.S. Pat. Nos. 5,032,390, 5,132,104, EPO 433 086 A1, U.S. Pat. Nos. 4,606,869, 3,397,257, 4,543,341, 4,808,398, 2,898,191, 4,9233,518, and 4,721,610), crystalline metal oxides (U.S. Pat. Nos. 5,093,099, 5,091,765, 4,261,965, 2,900,244, and 4,722,763), including crystalline whisker-shaped zinc oxide (U.S. Pat. No. 5,066,475), and needle-shaped zinc oxide particles (U.S. Pat. Nos. 5,102,650, 5,171,364 and 5,132,104). U.S. Pat. No. 5,066,475 relates to whiskers of zinc oxide having a crystal structure which includes a central body and four needle crystal projections radially extending therefrom, and is useful in reinforcing materials. U.S. Pat. No. 5,012,650 relates to needle-like electrically conductive zinc oxide filler which is useful for its low specific volume resistance and electrical conductivity. U.S. Pat. No. 5,132,104 discloses a method of preparing conductive needle-like zinc carbonate having an average length of 10-100 .mu.m, an average thickness of 0.5-10 .mu.m, and an aspect ratio of at least three. Electron micrographs of the needle-like zinc carbonate reveals a complex and highly disorganized matrix.
It is an object of the invention to provide fibers, e.g., as are used in textiles, such as carpets, upholstery, clothing, ropes, hairbrushes, wigs, etc., which possess conductive and antistatic properties. It is another object of the invention to provide antistatic fibers using zinc oxide rod particles which are ultra-fine enough to provide transparency and reflectivity, and thus to allow for color additives based on any desired color. Yet another object of the invention is to provide antistatic fibers which are highly conductive and yet are not brittle. It is another object of the invention to provide fibers for use in textiles containing zinc oxide rod-shaped particles of dimensions which allow the particles to form a conductive coating. It is also an object of the invention to provide fibers comprising zinc oxide rods which have a high enough ratio of surface area to volume or weight to retain inter-particle contact, and thus to retain conductivity and antistatic properties. Zinc oxide particles of the invention, because they are rod-shaped, may assume a side-by-side or end-on-end arrangement or a criss-cross packing arrangement, once the fiber is drawn into its desired length, such that there are relatively few gaps between the particles.